Method of forming truer

ABSTRACT

A method of forming a truer in a truing where a groove of a grinding wheel used for grinding a chamfer portion of a wafer is formed by a truer having a disc-shape, wherein the method comprising: a process A for adjusting a diameter and a rough shape of the truer by a master grinding wheel for forming the truer; and a process B for forming an edge of the truer into a target shape, wherein the process A and the process B are performed by a plurality of master grooves having different shapes from each other, the plurality of master grooves being provided with the master grinding wheel or the process A and the process B are performed by a plurality of portions having different shapes from each other in at least one of the plurality of master grooves provided with the master grinding wheel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent specification is based on Japanese patent application, No.2022-100214 filed on Jun. 22, 2022 in the Japan Patent Office, theentire contents of which are incorporated by reference herein.

PRIOR ART

[Patent Document 1] Japanese Unexamined Patent Application PublicationNo. 2005-153085

[Patent Document 2] Japanese Unexamined Patent Application PublicationNo. 2018-167331

[Patent Document 3] Japanese Unexamined Patent Application PublicationNo. 2021-181151

BACKGROUND OF THE INVENTION

The present invention relates to a truing of a chamfering device forprecisely chamfering an end surface of a plate shaped workpiece made ofvarious materials such as silicon, sapphire, compound and glass (inparticular, a semiconductor wafer and a glass panel) and relates to amethod of forming a truer used in a truing for forming working groovesof a grinding wheel which grinds and chamfers a plate-shaped workpiece.

Conventionally, when the plate-shaped workpiece such as thesemiconductor wafer is chamfered by grinding, the processing isperformed by pressing the grinding wheel on an outer peripheral portionof the workpiece. In general, the outer peripheral portion of thegrinding wheel is provided with the groove having the shape anddimension corresponding to the target shape of the plate-shapedworkpiece. The grinding of the outer peripheral portion of the workpieceis performed by an inner peripheral surface of the groove by insertingthe outer peripheral portion of the plate-shaped workpiece into thegroove. The shape and the dimension of the groove are changed and theinner peripheral surface of the groove is worn or damaged after thechamfering processing is repeated. Thus, the accuracy of the processingdeteriorates.

The chamfering processing is performed over a long period, it isnecessary to replace the grinding wheel or form the shape of thegrinding wheel again. Therefore, the grinding wheel is processed by atruing grinding wheel (truer). Namely, the truing is performed. In thetruing, the truing grinding wheel is ground in a state that the truinggrinding wheel is in contact with an inner peripheral surface of a totalform groove of a master grinding wheel, the total form groove having thetarget shape of the workpiece. The total form groove having the sameshape as the master grinding wheel is formed on the grinding wheel usedfor the actual chamfering processing by abutting the outer peripheralportion of the truing grinding wheel on the grinding wheel. The truinggrinding wheel is made of the material (e.g., GC wheel) which is harderthan the material (e.g., resin bond grinding wheel) of the grindingwheel used for the actual chamfering processing. The master grindingwheel is made of the material (e.g., metal bond grinding wheel) which isharder than the material of the truing grinding wheel.

As a method for truing the shape of the groove of a chamfering wheelused for a chamfering device for a plate-shaped workpiece into a desiredshape easily, the method of transferring the groove shape of the mastergrinding wheel to the outer periphery of the truing grinding wheel andtransferring the outer peripheral shape of the truing grinding wheel tothe chamfering wheel to form the groove on the chamfering wheel isconventionally known. For example, the above described method isdisclosed in Patent Document 1.

In a normal grinding, a chamfer portion is ground in a state that a mainsurface of the wafer is perpendicular to a rotation axis of a resingrinding wheel. In this case, grinding marks easily appear in acircumferential direction of the chamfer portion. A so-called helicalgrinding is known for grinding the chamfer portion of the wafer in astate that a resin bond grinding wheel is inclined with respect to thewafer.

In the helical grinding, when the formation or the correction (truing)of the groove is performed on the resin grinding wheel by using thetruer having the end portion which is formed symmetrically in thevertical direction, a twist occurs in the truer since the resin grindingwheel is inclined. Thus, the groove of the resin grinding wheel isasymmetrically formed in the vertical direction. Patent Document 2discloses the method of processing the upper part or the lower part inthe expected position of the groove by the truer having the thicknesssmaller than the width of the groove of the grinding wheel for grindingthe chamfer portion of the wafer and then relatively lowering or raisingthe truer in the thickness direction with respect to the grinding wheel.Thus, the transfer rate and the workability are improved in the truingand the accuracy of the groove formed by the truer is improved.

Patent Document 3 discloses the method of relatively moving the grindingwheel with respect to the workpiece so that the contact portion betweenthe workpiece and the protruded grinding portion located at the outerperipheral portion of the grinding wheel is moved in accordance with themovement conditions calculated based on the curvature radius of anarc-shaped portion of the grinding wheel for performing the chamferingprocessing easily, efficiently and precisely with a simple structure forsupporting and driving the workpiece and the grinding wheel and formingthe shape of the grinding wheel easily.

SUMMARY OF THE INVENTION

In the above described conventional technology, Patent Document 1 usesthe method where the shape of the groove of the master grinding wheel,which is the grinding wheel for forming the truer, is transferred to theedge of the truer as it is by cutting the truer with the groove of themaster grinding wheel. Thus, only one kind of shape can be formed by onegroove of the master grinding wheel. Accordingly, it is difficult tochange the shape of the truer. It is impossible to change the shape whenthe processing conditions of the chamfering device (e.g., settings ofrotation axis of grinding wheel) are changed.

In the methods described in Patent Documents 2 and 3, although the shapeof the truer can be changed, the shape cannot be corrected precisely toobtain a desired processing shape and the accuracy of the edge shape ofthe truer cannot be further improved.

The present invention reduces time and cost for forming the truer andachieves quality uniformity. Furthermore, the present invention improvesthe transfer rate and the workability in the truing and improves theaccuracy of the groove formed on the truer. In particular, the presentinvention improves the precision of an edge shape of the truer. Thus,the present invention further improves the dimensional accuracy of thegroove shape and the angle of the groove of the outer periphery grindingwheel to which the shape of the truer is transferred. In addition, thepresent invention prevents the corner of the end portion from beingrounded. Accordingly, the accuracy of the finally chamfered shape isimproved.

The configurations of the present invention for achieving the abovedescribed purposes are as follows.

[1] A method of forming a truer in a truing where a groove of a grindingwheel used for grinding a chamfer portion of a wafer is formed by atruer having a disc-shape, wherein the method comprising: a process Afor adjusting a diameter and a rough shape of the truer by a mastergrinding wheel for forming the truer; and a process B for forming anedge of the truer into a target shape, wherein the process A and theprocess B are performed by a plurality of master grooves havingdifferent shapes from each other, the plurality of master grooves beingprovided with the master grinding wheel or the process A and the processB are performed by a plurality of portions having different shapes fromeach other in at least one of the plurality of master grooves providedwith the master grinding wheel.

[2] The method of forming the truer of [1], wherein the process A andthe process B are performed by a first groove and a second groove whichare the plurality of master grooves having different shapes from eachother, the first groove and the second groove being provided with themaster grinding wheel.

[3] The method of forming the truer of [2], wherein an edge processingis performed by using an end portion of the second groove after thetruer is processed by the first groove.

[4] The method of forming the truer of [2], wherein a radius of anarc-shaped portion of an end portion of the second groove is larger thana radius of an arc-shaped portion of an end portion of the first groove.

[5] The method of forming the truer of any one of [2] to [4], wherein achamfering processing of the truer is performed by at least one of theplurality of master grooves by moving the truer in a direction ofseparating from at least one of the plurality of master grooves.

[6] The method of forming the truer of [3], wherein a corner Rprocessing of the truer is performed by using the end portion of thesecond groove for adjusting a shape, a radius and a roundness of thecorner of the truer while reducing a moving distance of the truer.

[7] The method of forming the truer of [6], wherein the corner Rprocessing of a lower surface of the truer is performed after the cornerR processing of an upper surface of the truer is performed.

[8] The method of forming the truer of [7], wherein parameters of amovement start position, a machining speed, an escape position, anescape speed, a rotation speed of the truer, a machining start point anda machining end point are determined by using the value of the corner Rprocessing of the upper surface and the value of the corner R processingof the lower surface, the movement start position including an enteringpoint and an entering speed.

[9] The method of forming the truer of [8], wherein an amplitude, themachining speed, a spark-out time and the number of times ofreciprocating motion are specified as a traverse motion independentlyfor the corner R processing of the upper surface and the corner Rprocessing of the lower surface.

[10] The method of forming the truer of [1], wherein the process A andthe process B are performed by using the plurality of portions havingdifferent shapes from each other in at least one of the plurality ofmaster grooves provided with the master grinding wheel, and the processB is performed by using an end portion of at least one of the pluralityof master grooves.

[11] The method of forming the truer of [10], wherein the process A isperformed by using a bottom portion of at least one of the plurality ofmaster grooves.

[12] A master grinding wheel of forming a truer for forming a groove ofa grinding wheel used for grinding a chamfer portion of a wafer, themaster grinding wheel comprising: a first groove for adjusting adiameter and a rough shape of the truer; and a second groove for formingan edge of the truer into a target shape, the second groove beingdifferent from the first groove.

[13] A master grinding wheel of forming a truer for forming a groove ofa grinding wheel used for grinding a chamfer portion of a wafer, whereinat least one master groove of the master grinding wheel comprising: afirst portion for adjusting a diameter and a rough shape of the truer;and a second portion for forming an edge of the truer into a targetshape, the second portion being different from the first portion.

The present invention reduces time and cost for forming the truer andachieves quality uniformity. Furthermore, the present invention improvesthe transfer rate and the workability in the truing and improves theaccuracy of the groove formed on the truer. In particular, the presentinvention further improves the precision of the edge shape of the truer.Thus, the present invention improves the dimensional accuracy of thegroove shape and the angle of the groove of the outer periphery grindingwheel to which the shape of the truer is transferred. In addition, thepresent invention prevents the corner of the end portion from beingrounded. Accordingly, the accuracy of the finally chamfered shape isimproved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view showing a main part of a chamfering deviceconcerning an embodiment of the present invention.

FIG. 2 is a side view showing a truing process in an embodiment of thepresent invention.

FIGS. 3A and 3B are side views showing a state that a wafer W isprocessed by a grinding wheel 55 formed in a recessed groove in anembodiment of the present invention.

FIGS. 4A and 4B are side views showing a method of forming a truer 41 inan embodiment of the present invention.

FIGS. 5A to 5C are side views showing a precise machining performed by asecond groove 62 in an embodiment of the present invention.

FIG. 6 is a flowchart showing procedures of a forming processing of thetruer 41 in an embodiment of the present invention.

FIG. 7 is a flowchart showing procedures of an edge processing shown inFIG. 6 in an embodiment of the present invention.

FIGS. 8A to 8G are explanation drawings showing procedures of a formingprocessing of the truer 41 in an embodiment (second embodiment) of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

Hereafter, an embodiment (first embodiment) of the present inventionwill be explained in detail referring to the drawings. FIG. 1 is a frontview showing a main part of a wafer chamfering device concerning anembodiment of the present invention. A wafer chamfering device 10comprises a wafer feeding unit 20, a grinding wheel rotating unit 50, anot-illustrated wafer supplying/housing portion, a not-illustrated wafercleaning/drying portion, a not-illustrated wafer transferring unit and acontroller for controlling the operations of the components of the waferchamfering device, for example.

The wafer feeding unit 20 includes an X-axis base 21 placed on a bodybase 11, two X-axis guide rails 22, four X-axis linear guides 23 and anX table 24 which is moved in the X-direction shown in the figure by anX-axis driving mechanism 25 comprised of a ball screw and a steppingmotor.

The X table 24 incorporates two Y-axis guide rails 26, four Y-axislinear guides 27 and a Y table 28 a which is moved in the Y-directionshown in the figure by a not-illustrated Y-axis driving mechanismcomprised of a ball screw and a stepping motor.

The Y table 28 incorporates two Z-axis guide rails 29 and a Z table 31which is moved in the Z-direction in the figure by a Z-axis drivingmechanism 30 guided by not-illustrated four Z-axis linear guides andcomprised of a ball screw and a stepping motor.

The Z table 31 a θ-axis motor 32 and a θ spindle 33. A wafer table 34 onwhich the wafer W (plate-shaped workpiece) is placed and sucked isattached to the θ spindle 33. The wafer table 34 is rotated in the θdirection shown in the figure around the rotation axis CW of the wafertable.

The wafer W and a truer 41 are rotated in the θ direction and moved inthe X, Y and Z directions shown in the figure by the wafer feeding unit20.

The grinding wheel rotating unit 50 includes a circumferential grindingspindle 51 on which a circumferential rough grinding wheel 52 isinstalled, a circumferential fine grinding spindle 54 and acircumferential fine grinding motor 56 which are installed on aturntable 53 arranged on an upper part. The circumferential grindingspindle 51 is driven by a not-illustrated circumferential grinding wheelmotor to rotate around an axial center.

A grinding wheel 55, which is a chamfering wheel for performingfinish-grinding on an outer periphery of the wafer W, is installed onthe circumferential fine grinding spindle 54. The circumferential finegrinding spindle 54 performs the finish processing for chamfering theouter periphery of the wafer W in a state that the rotation axis of thecircumferential fine grinding spindle 54 is inclined 3 to 15°,preferably 6 to 10° with respect to the rotation axis of the wafer W.The helical grinding is performed as described above. Although slightgrinding marks are generated on the chamfer portion of the wafer W in anoblique direction, the effect of improving the surface roughness of thechamfer portion can be obtained compared to the normal grinding.

The wafer processing is performed in the order of slicing, chamfering,lapping, etching, donor killer and precise chamfering. Various cleaningsare performed between the above described steps to remove the cut waste.The material such as silicon is hard and brittle. If the end surface ofthe wafer remains sharp after the slicing, the wafer is easily crackedor chipped when transferring or positioning the wafer in the subsequentprocessing. The pieces of the cracked or chipped wafer may damage orstain the surface of the wafer. In order to prevent the above describedproblem, the chamfering processing is performed for chamfering the endsurface of the sliced wafer by the chamfering wheel coated with diamond.

The grinding wheel 55 used here is made of metal powder such as Fe, Crand Cu as a main component of abrasive grain and is formed by mixingdiamond abrasive grain, for example. The binder of the grinding wheel 55is made of phenol resin, epoxy resin, polyimide resin, polystyrene resinor polyethylene resin as a main component and is preferably formed bymixing diamond abrasive grain or cubic boron nitride abrasive grain, forexample.

In addition, the grinding wheel 55 used here is the resin bond grindingwheel using the diamond abrasive grain having the diameter of 50 mm andthe grain size of #3000. The circumferential fine grinding spindle 54 isthe spindle driven by a built-in motor using air bearing and is rotatedat the rotation speed of 35000 rpm.

FIG. 2 is a side view showing the truing process. The working groove forthe chamfering processing is formed on the grinding wheel 55 by thetruer 41. The truer 41 having a disc-shape is installed on a lowerportion of the wafer table 34 so that the truer 41 is coaxially with arotation axis of the wafer table. Thus, the truer is rotated by thewafer table 34. The outer peripheral portion of the truer 41 ispreliminarily chamfered by the master grinding wheel (shown in FIGS. 3Aand 3B). Namely, the working groove for the chamfering processing isformed on the grinding wheel 55 by using the truer 41 in a state thatthe cross-sectional shape of the master grinding wheel (shown in FIGS.3A and 3B) is transferred to the outer peripheral portion of the truer41.

The truer 41 is preferably formed by combining abrasive grain made ofsilicon carbide by using the phenol resin while adding a filler ifrequired and forming the combined material into the truer 41 having adisc-shape, for example. In addition, the truer 41 has the outerdiameter equal to or smaller than the size of the wafer W, has the samethickness as the thickness of the wafer W and has a disc-shape. Thetruer 41 can be a GC (Green silicon carbide) wheel or WA (White fusedalumina) wheel. It is preferable that the grain side of the grindingwheel is approximately #320.

FIGS. 3A and 3B are side views showing a state that the wafer W isprocessed by the grinding wheel 55 formed in a recessed groove. If thelinear portion is processed by the protruded grinding wheel shown inPatent Document 3, the processing is performed by a point contact. Thus,uneven abrasion is generated on the grinding wheel and the machininglocus appears as the streak. Accordingly, the surface roughnessdeteriorates and the processing time becomes long. In addition, if theprocessing is performed by the point contact of the protruded grindingwheel, the processing time becomes long and the processing stressescapes. Thus, it is difficult to form the target shape.

On the other hand, as shown in FIG. 3A, when a rough shape is formed bythe recessed groove (recessed grinding wheel), the processing stresshardly escapes by cancelling the stresses of the upper inclined surfaceand the lower inclined surface. Thus, the shape hardly becomes bad evenwhen forming the linear portion. In addition, the line contact ispossible also at the linear portion when processed by the recessedgroove. Accordingly, the processing time is short, the streak does notappear, the surface roughness is improved, the processing load isreduced and the wheel life is improved remarkably.

FIG. 3B shows the state that an arbitrary finished shape is formed byusing an end portion shown by the arrow mark A which does not contributeto the processing of the diameter and the rough shape in the grindingwheel 55. Although the portion of the arrow mark A is shown by astraight line in the figure, this portion can also include a curved line(surface). Because of this, the shape, the radius, the roundness and thelike of the corner portion can be formed more accurately. At this time,as shown by the arrow mark B, when the wafer W is moved in a pullingdirection which is the direction of separating from the grinding wheel55, the contact area between the wafer W and the grinding wheel 55becomes larger. Thus, the processing load is reduced and the wheel lifebecomes long. In addition, if the difference between the shape beforethe processing and the target shape is large, the grinding amount groundby the end portion increases and the abrasion of the grinding wheel 55 bincreases. Thus, it is preferable to preliminarily make the groove shapeof the grinding wheel 55 close to the target shape.

FIG. 4A is a side view showing a method of forming the truer 41. Amaster grinding wheel 60 for forming the truer 41 includes a pluralityof grooves (first groove 61, second groove 62) as the master grooves.The first groove 61 is used for adjusting the diameter and the roughshape of the truer 41. The first groove 61 can be the total form groove.In addition, the adjustment of the diameter and the rough shape adjustedby the first groove 61 can be the transferring of the grove shape of thefirst groove 61 to the truer 41. On the other hand, the second groove 62is used for adjusting the edge of the truer 41 into a target shape(arbitrary and desired cross-sectional shape). The second groove 62includes the arc-shaped (round-shaped, R-shaped) portion having a largerradius at the end portion (opening portion). Namely, the shapes of thefirst groove 61 and the second groove 62 are different from each other.When the arc-shaped portion of the second groove is used, the truer 41having an arbitrary cross-sectional shape can be obtained although thearbitrary cross-sectional shape cannot be obtained merely bytransferring the groove shape.

FIG. 4B is an enlarged view of the second groove 62. The second groove62 includes a linear portion 81 which is approximately parallel to thethickness direction (Z-direction) of the master grinding wheel 60, upperand lower inclined portions 82 which are extended from the end portionof the linear portion 81, and upper and lower arc-shaped portions 83having a curved line extended from the end portion of each of theinclined portions 82 to the opening portion. Although the second groove62 shown in FIG. 4B includes the linear portion 81, the inclinedportions 82 and the arc-shaped portions 83, the second groove 62 is notlimited to the configuration shown in FIG. 4B. It is enough if thesecond groove 62 includes the linear portion 81 and the arc-shapedportions 83. Although the linear portion 81 and the inclined portions 82are shown by straight lines (in the cross-sectional shape), the linearportion 81 and the inclined portions 82 can include curved lines (curvedsurfaces).

The master grinding wheel 60 is rotated at the rotation speed of 8000rpm, for example. In this state, the Z table 31 is moved by the Z-axisdriving mechanism 30 so that the height of the truer 41 is aligned withthe height of each of the grooves of the master grinding wheel 60.

Then, the Y table 28 is moved toward the master grinding wheel 60. Whenthe Y table 28 is moved in the Y-direction, the outer peripheral portionof the truer 41 is cut in the master groove of the master grinding wheel60 and the wafer table 34 is slowly rotated by the θ-axis motor 32 forone revolution. Thus, the outer peripheral portion of the truer 41 ischamfered and the shape of the master groove is transferred to the outerperipheral portion of the truer 41. Then, the truer 41 is moved in thedirection of separating from the master grinding wheel 60. Thus, thetransfer from the cross-sectional shape of the master groove to thecross-sectional shape of the outer peripheral portion of the truer 41 isfinished.

The transferring method from the master groove to the truer 41 (i.e.,the forming processing of the truer 41) is as follows. First, asdescribed above, the outer peripheral portion of the truer 41 is cut inthe first groove 61 as shown in the arrow mark D for adjusting thediameter and the rough shape of the truer 41. Then, the edge processingincluding the adjustment to an accurate and arbitrary cross-sectionalshape is performed by mainly using the arc-shaped portions 83 of thesecond groove 62.

FIGS. 5A to 5C are side views showing a precise machining performed bythe second groove 62. FIG. 6 is a flowchart showing procedures of theforming processing of the truer 41. FIG. 7 is a flowchart showingdetailed procedures of the edge processing in FIG. 6 (Step 4 in FIG. 6). The outline of the forming processing of the truer 41 shown in FIG. 6is (1) input of various conditions (Step 1), (2) calculation of theprocessing conditions (machining start point, machining end point) ofthe chamfering device based on the various input conditions (Step 2),(3) forming processing of the truer 41, mainly diameter processing (Step3) and (4) edge processing (Step 4).

Steps 1, 2

The various conditions to be inputted as parameters are a diameter, achamfering angle, an end shape (straight line length m, surface width n,size of the corner R of the end portion), a movement start position(entering point, entering speed), a chamfering speed, a machining speedof the roundness of the corner, an escape position, an escape speed, arotation speed of the truer 41 and a rotational speed of the mastergrinding wheel 60, for example.

The chamfering method using the chamfering device includes the transferof the shape of the master groove shown in Step 3 below and theadjustment to an arbitrary shape shown in Step 4 below using thearc-shaped portion of the master groove (second groove). Therefore, anexample of the conditions inputted in this step can be the data of anarbitrary and desired cross-sectional shape. The desired cross-sectionalshape can be the total form groove. It is preferred that the desiredcross-sectional shape is smaller than the cross-sectional shape afterbeing ground by the first groove 61. The desired cross-sectional shapecan be an arbitrary shape without depending on the groove shapes of thefirst groove 61 and the second groove 62. Note that the processingconditions calculated by the chamfering device are mainly the machiningstart point and the machining end point.

Step 3: Process A

Step 3 is the process of adjusting the diameter and the rough shape ofthe truer (process A). This step is performed by using the first groove61. In this step, the master grinding wheel 60 is rotated at therotation speed of 8000 rpm, for example. The height of the truer 41 isaligned with the height of the master groove (first groove 61) of themaster grinding wheel 60 and the processing is started. The truer 41 ismoved toward the master grinding wheel 60 as shown in the arrow mark D,and the outer peripheral portion of the truer 41 is cut in the mastergroove (first groove 61) of the master grinding wheel 60. Thus, the endsurface of the outer peripheral portion of the truer 41 is mainlychamfered. In the diameter processing, the parameters of the processingconditions are determined by using two types of values: one is the valueof the corner R processing (upper surface) and the other is the value ofthe corner R processing (lower surface). As one embodiment, the corner Rprocessing of the lower surface is performed after the corner Rprocessing of the upper surface is performed.

As described above, the adjustment of the diameter and the rough shapeis performed by using the recessed groove in this method. Thus, thepoint contact between the master grinding wheel and the truer is avoidedand the processing stress hardly escapes. As a result, the grindingprocess can be performed efficiently.

Step 4: Steps 401 to 407 in Detail: Process B

Step 4 is the process of forming the edge of the truer into a targetshape (process B). The processing of this step is performed by using thesecond groove 62 having different (cross-sectional) shape from the shapeof the first groove 61. “The second groove 62 having different shapefrom the shape of the first groove 61” means a state that the arc-shapedportion is provided at the end portion (near the opening portion) of thesecond groove 62 as one embodiment. The other shapes than the arc-shapedportion can be also used as long as the shape is different from theshape used in the process A. In the flowchart, specifically, after thediameter and the rough shape are formed by the first groove 61, thetruer 41 is moved to the movement start position where the height of thetruer 41 is aligned with the height of the second groove 62 as shown inFIG. 5A (Step 401).

The chamfering device specifies the parameters of the processingconditions based on the various conditions (e.g., data of desiredcross-sectional shape) inputted beforehand (Step 402). Then, the truer41 moves to the entering point at a predetermined entering speed (Step403). The rotation of the truer 41 is started (Step 404) and the portionshown by the bold line in FIG. 5B is chamfered at a predeterminedchamfering angle (Step 405). At this time, since the second groove 62 isthe recessed groove, the processing is performed in the line contactstate. Accordingly, the processing time is short, the streak does notappear, the surface roughness is improved and the processing load isreduced. In addition, it is preferred that the chamfering processing isperformed in the direction of pulling the truer 41 (direction ofseparating from the groove) as shown in the arrow mark B in FIG. 5C forreducing the processing load.

After the chamfering processing, the corner R processing is performedfor processing the more detailed portions while reducing the movingdistance (i.e., machining feed amount) of the truer 41 (Step 406).Specifically, the corner R processing for forming the shape, the radius,the roundness and the like of the corner portion is performed. Thecorner R processing (upper surface) is performed by using the endportion of the second groove 62 having the arc-shaped portion shown bythe arrow mark A which does not contribute to the processing of thediameter. The radius of the arc-shaped portion of the end portion of thesecond groove 62 is larger than the radius of the arc-shaped portion ofthe end portion of the first groove 61. Accordingly, the shape, theradius and the roundness of the corner portion of the truer 41 can beprocessed more accurately, the streak does not appear and the surfaceroughness is improved.

After the corner R processing (upper surface) is finished, the truer 41is moved to the movement start position for performing the corner Rprocessing (lower surface) in Step 401. Then, Step 401 to Step 405 arerepeated similarly. In addition, the parameters such as the movementstart position (entering point, entering speed), the escape position,the machining speed, the escape speed, the rotation speed of the truer41, the machining start point, the machining end point are determined byusing two types of values: one is the values of the corner R processing(upper surface) and the other is the corner R processing (lowersurface).

It is preferred that the amplitude, the machining speed, the spark-outtime, the number of times of reciprocating motion are specified as atraverse motion independently for each process for improving the surfaceroughness. Note that the spark-out means the operation of continuing thegrinding without cutting at the end of the grinding operation. Theprocessing is advanced by a minute amount.

When a predetermined width of the circumferential surface, apredetermined circumferential angle or a predetermined circumferentialshape are not satisfied due to the reduction of the grinding ability,the correction (truing) of the groove of the grinding wheel 55 isappropriately performed by using the truer 41. At this time, when thetruing of the present invention is performed, the number of the waferscapable of being processed by one truing increases and life becomes longeven if the resin grinding wheel is used. The number of wafers capableof being processed by one resin grinding wheel increases. Accordingly,it is also possible to reduce the cost for manufacturing thesemiconductor wafer.

In the present embodiment, it is not required to use another grindingwheel (groove) for forming the truer even when the grinding wheel 55 ischanged to the other shape. Accordingly, the present embodiment canimprove the accuracy of the grinding wheel 55 and eliminate thereplacement operation or new creation of the grinding wheel. Thus, thecost can be reduced and the time from the order to the manufacturer ofthe grinding wheel to the delivery of the grinding wheel can be shortencompared to the case where the grinding wheel is newly manufactured.

Second Embodiment

Hereafter, the second embodiment of forming the diameter and the roughshape and adjusting to an arbitrary shape (edge processing) by using thesecond groove 62 will be explained. Note that the explanation of thewafer chamfering device and the like to be used is omitted since theyare same as the first embodiment. Hereafter, the difference from thefirst embodiment will be mainly explained.

FIGS. 8A to 8G are explanation drawings showing the procedures of theforming processing of the truer 41 performed by using the second groove62 in the present embodiment. First, FIG. 8A shows the state before thetruer 41 is processed. In the following processes, the diameter and therough shape of the truer 41 are adjusted to a cross-sectional shape 84.

Note that the drawings are schematically shown. The shapes areexaggeratingly shown for clearly explaining the difference before andafter the truer 41 is processed. Although the object to be processed(ground) is the truer 41 in FIGS. 8A to 8G, this method can be alsoapplied to the grinding of the wafer and the like without being limitedto the truer 41.

FIG. 8B shows the state that the truer is cut in the rotating mastergrinding wheel 60 for adjusting the diameter and the rough shape of thetruer 41 into the cross-sectional shape 84 (process A). At this time,the end portion of the truer 41 is contacted with the linear portion 81and the inclined portion 82, which are the bottom portion of the secondgroove 62 of the master grinding wheel, and the truer 41 is ground. Inother words, the process A is performed by using the linear portion 81and the inclined portion 82 which are the bottom portion of the secondgroove 62 in the present embodiment. The linear portion 81 and theinclined portion 82 have the similar function as the already explainedrecessed groove such as the first groove 61. It is possible to adjustthe diameter and the rough shape of the truer 41 in almost the linecontact state so that stress does not escape.

After the rough shape is adjusted and the cross-sectional shape of thetruer 41 becomes the state shown as 84, the edge processing is performedby the arc-shaped portions 83 (process B). The process B is performed byusing the portion which is different from the portion used for theprocess A and this portion has the different shape from the shape of theportion used for the process A. Specifically, the process B is performedby using the arc-shaped portions 83 located at the end portion (endportion in the opening direction) of the second groove 62.

The linear portion 81 and the inclined portion 82 used in the process Ahave the function of the recessed groove as described above. Therecessed groove can form the rough shape efficiently by contacting withthe truer 41 in the line contact state so that stress does not escape.In other words, the groove shape can be easily transferred to the truer41.

On the other hand, the arc-shaped portions 83 used in the process B havea convex shape protruded toward the inside of the groove. Thus, theshape is different from the linear portion 81 and the inclined portion82 which are linearly formed. When the truer 41 is in contact with thearc-shaped portions 83, an arbitrary shape can be formed in accordancewith the position of the truer and the manner of the contact.

The explanation of the steps will be restarted here. After, the diameterand the rough shape are adjusted, the truer 41 is moved in the Z (−)direction along the arc-shaped portions 83 located in the Z (−)direction of the second groove 62 while separating from the linearportion 81 and the inclined portion 82 (for changing the position to beused). The arrow mark shown in FIG. 8B shows the moving direction of thetruer 41.

The edge processing of the truer 41 is performed while moving along thearc-shaped portions 83. FIG. 8C and 8D show the state of the edgeprocessing processed by the arc-shaped portions 83. In this process, theedge shape and the like are adjusted by moving (reciprocating ifrequired) the truer 41 along the arc-shaped portions 83 based on thedata of the desired cross-sectional shape received in the Step 1 of FIG.6 as described above. Typically, the arc-shaped portions 83 arepreferably not in contact with the truer 41 in the process (process A)of adjusting the diameter and the rough shape. Since the arc-shapedportions 83 have a curved shape, it is easy to adjust thecross-sectional shape arbitrarily in accordance with the manner ofabutting the truer 41 (i.e., manner of moving the truer 41 in Y-axis andZ-axis directions) (process B).

Then, similarly, as shown in FIG. 8E and FIG. 8F, the shape of (mainly)the upper end side of the truer 41 is adjusted by moving the truer 41along the arc-shaped portion 83 located at the upper (Z (+)) side of thesecond groove 62. Although the lower surface of the truer 41 isprocessed in advance in the present embodiment, it is also possible toprocess the upper surface of the truer 41 in advance as alreadyexplained.

FIG. 8G shows the truer 41 after the edge processing is finished. Across-sectional shape 85 of the truer 41 after the above describedadjustment can have the different shape from 84 whose diameter and roughshape are adjusted by the linear portion 81 and the inclined portion 82.In other words, this method enables to adjust the diameter and the roughshape and further enables the processing to obtain an arbitrarycross-sectional shape by using the second groove 62.

In the conventional method of forming the truer using the mastergrinding wheel, the shape of the master groove is transferred to thetruer and thus the shape of individual master groove corresponds to thecross-sectional shape of the individual truer. Therefore, when adjustingthe shape of a plurality of truers into a different cross-sectionalshape, a plurality of master grinding wheels is prepared and replaced totransfer the shape of each master grinding wheel or a master grindingwheel having a plurality of master grooves is used to transfer the shapeof each master groove.

However, by using the method of the present invention, even when aplurality of master grinding wheels or a plurality of master grooves isnot used, the cross-sectional shape of the truer can be arbitrarilyadjusted by using the master groove having the arc-shaped portion at theopening portion.

DESCRIPTION OF THE REFERENCE NUMERALS

10: wafer chamfering device, 11: body base, 20: wafer feeding unit, 21:X-axis base, 22: X-axis guide rail, 23: X-axis linear guide, 24: Xtable, 25: X-axis driving mechanism, 26: Y-axis guide rail, 27: Y-axislinear guide, 28: Y table, 29: Z-axis guide rail, 30: Z-axis drivingmechanism, 31: Z table, 32: θ-axis motor, 33: θ spindle, 34: wafertable, 41: truer, 50: grinding wheel rotating unit, 51: circumferentialgrinding spindle, 52: circumferential rough grinding wheel, 53:turntable, 54: circumferential fine grinding spindle, 55: grindingwheel, 56: circumferential fine grinding motor, 60: master grindingwheel, 61: first groove, 62: second groove, 81: linear portion, 82:inclined portion, 83: arc-shaped portion, 84: cross-sectional shape, 85:cross-sectional shape, CW: rotation axis of wafer table, GC: disc-shape,W: wafer, n: surface width

1. A method of forming a truer in a truing where a groove of a grindingwheel used for grinding a chamfer portion of a wafer is formed by atruer having a disc-shape, wherein the method comprising: a process Afor adjusting a diameter and a rough shape of the truer by a mastergrinding wheel for forming the truer; and a process B for forming anedge of the truer into a target shape, wherein the process A and theprocess B are performed by a plurality of master grooves havingdifferent shapes from each other, the plurality of master grooves beingprovided with the master grinding wheel or the process A and the processB are performed by a plurality of portions having different shapes fromeach other in at least one of the plurality of master grooves providedwith the master grinding wheel.
 2. The method of forming the trueraccording to claim 1, wherein the process A and the process B areperformed by a first groove and a second groove which are the pluralityof master grooves having different shapes from each other, the firstgroove and the second groove being provided with the master grindingwheel.
 3. The method of forming the truer according to claim 2, whereinan edge processing is performed by using an end portion of the secondgroove after the truer is processed by the first groove.
 4. The methodof forming the truer according to claim 2, wherein a radius of anarc-shaped portion of an end portion of the second groove is larger thana radius of an arc-shaped portion of an end portion of the first groove.5. The method of forming the truer according to claim 2, wherein achamfering processing of the truer is performed by at least one of theplurality of master grooves by moving the truer in a direction ofseparating from at least one of the plurality of master grooves.
 6. Themethod of forming the truer according to claim 3, wherein a corner Rprocessing of the truer is performed by using the end portion of thesecond groove for adjusting a shape, a radius and a roundness of thecorner of the truer while reducing a moving distance of the truer. 7.The method of forming the truer according to claim 6, wherein the cornerR processing of a lower surface of the truer is performed after thecorner R processing of an upper surface of the truer is performed. 8.The method of forming the truer according to claim 7, wherein parametersof a movement start position, a machining speed, an escape position, anescape speed, a rotation speed of the truer, a machining start point anda machining end point are determined by using the value of the corner Rprocessing of the upper surface and the value of the corner R processingof the lower surface, the movement start position including an enteringpoint and an entering speed.
 9. The method of forming the trueraccording to claim 8, wherein an amplitude, the machining speed, aspark-out time and the number of times of reciprocating motion arespecified as a traverse motion independently for the corner R processingof the upper surface and the corner R processing of the lower surface.10. The method of forming the truer according to claim 1, wherein theprocess A and the process B are performed by using the plurality ofportions having different shapes from each other in at least one of theplurality of master grooves provided with the master grinding wheel, andthe process B is performed by using an end portion of at least one ofthe plurality of master grooves.
 11. The method of forming the trueraccording to claim 10, wherein the process A is performed by using abottom portion of at least one of the plurality of master grooves.
 12. Amaster grinding wheel of forming a truer for forming a groove of agrinding wheel used for grinding a chamfer portion of a wafer, themaster grinding wheel comprising: a first groove for adjusting adiameter and a rough shape of the truer; and a second groove for formingan edge of the truer into a target shape, the second groove beingdifferent from the first groove.
 13. A master grinding wheel of forminga truer for forming a groove of a grinding wheel used for grinding achamfer portion of a wafer, wherein at least one master groove of themaster grinding wheel comprising: a first portion for adjusting adiameter and a rough shape of the truer; and a second portion forforming an edge of the truer into a target shape, the second portionbeing different from the first portion.